1. Field of the Invention
The present invention relates to an ink-jet head for discharging ink to make recording, a substrate for use with the same head and an ink-jet recording apparatus.
2. Related Background Art
The ink-jet recording style disclosed in U.S. Pat. No. 4,723,129 or U.S. Pat. No. 4,740,796 enables high precision and high image quality recording at high speed and high density and suits for coloring and compacting. An ink-jet recording apparatus making use of this ink-jet recording style for bubbling ink with the aide of thermal energy and for discharging the ink to a recording medium generally comprises an ink-jet head substrate with heat generating resistors for bubbling the ink and wires for effecting an electric connection thereto fabricated on one and the same substrate to make an ink-jet recording head usable substrate and further a nozzle for discharging the ink formed thereon.
And, to save the electric energy to be invested on one hand and on the other hand, to prevent a decrease in the service life of the substrate both due to the mechanical damage accompanying the bubbling of ink and due to the breakage of a heater section on action of heating pulses, various contrivances are made to this ink-jet recording head substrate. Above all, with respect to a protective film for protecting the heating resistor having a heat generating section positioned between a pair of wiring patterns from the ink, many contrivances are accomplished.
From the viewpoint of thermal efficiency, higher thermal conductivity or a thinner film is advantageous in this protective film. On the other hand, however, the protective film serves to protect the wires connected to a heat generating body from the ink, a thicker film is advantageous if considered from the probability of defects in the film. From the competitive viewpoint of energy efficiency and reliability, the film thickness is set to the most suitable value. Incidentally, the protective film is subject to both cavitation damages, i.e. mechanical damages, due to the bubbling of ink and damages due to the chemical reaction with an ink component at higher temperatures, originating in that the surface after the bubbling reaches high temperatures.
For this reason, an insulating film for protecting the wire and a film stable against mechanical and chemical damages are hardly compatible in practice and therefore it is general to form a film stable against mechanical and chemical damages due to the bubbling of ink at the upper layer and to form an insulating film for protecting the wire at the lower layer. To be specific, it is general to form a Ta film, extremely high in mechanical and chemical stability, at the upper layer and to form an SiN film or an SiO film, whose stable film can be easily formed in an existing semiconductor device, at the lower layer.
To give a detailed account, a SiN film is formed on the wire as the protective film at a thickness of approximately 0.2 to 1 xcexcm and then an upper protective film, generally, a Ta film referred to as anti-cavitation film in view of function as a film against the cavitation damage, is formed at a thickness of 0.2 to 0.5 xcexcm. According to this configuration, compatibility between the life of a heat generating resistance in the ink-jet head substrate and the reliability is intended.
Besides, in addition to mechanical and chemical damages as mentioned above, there occurs a phenomenon that coloring materials, contaminants and suchlike contained in the ink are decomposed by heating to higher temperatures at the level of molecules to make a difficult-to-dissolve substance at the heat generating section, which is physically adsorbed to the anti-cavitation film serving as an upper protective film. This phenomenon is known as kogation (hereinafter, referred to as xe2x80x9ckoge.xe2x80x9d). When difficult-to-dissolve organic or inorganic substances are adsorbed onto the anti-cavitation film like this, thermal conduction from the heat generating resistance to the ink becomes non-uniform and the bubbling is instabilized. Thus, it is necessary that no xe2x80x9ckoge.xe2x80x9d occurs on the anti-cavitation film in the heat generating section, but the above described Ta film is generally adopted as a film relatively good in koge.
Meanwhile, in recent years, a leapt improvement in the performance of an ink-jet printer is demanding not only for an improvement in the performance of ink, e.g. the prevention of bleeding (blotting between the different color ink types) corresponding to high speed recording but also for an improvement in color development and weather resistance corresponding to higher image quality. For this reason, various components are added in ink and various components come to be added in each of three ink colors, Yellow, Magenta and Cyan, ink types forming a color image.
As a result of this, for example, in an ink-jet head with tricolor heat generating sections of Y, M and C and a Ta film as the upper protective film thereof formed on one and the same substrate, a difference in the ink constituents causes a corrosion even for the Ta film that has been considered to be stable before in the heat generating section corresponding to a certain color, thereby further resulting in the occurrence of a phenomenon that even the lower protective layer and the heat generating body are also damaged and broken. In case of using ink containing a divalent metallic salt such as Ca or Mg or the component forming a chelate complex, for example, the Ta film is liable to be corroded by thermochemical reaction with the ink.
On the other hand, as corresponds to this improvement in ink constituents, other anti-cavitation film have been developed. When the Ta-containing amorphous alloy exemplified in the Japanese Patent No. 2,683,350 of the present inventor is used, for example, in place of the Ta film, hardly any damage is confirmed to be effected even if any strongly corrosive substance is contained in an ink constituent.
Thus, use of a Ta-containing amorphous alloy can be examined as the upper protective film of the heat generating section in an ink-jet head capable of ejecting tricolor ink types of Y, M and C as mentioned above, but this Ta-containing amorphous alloy film is hardly subject to damages in surface in return for a high ink corrosion resistance, so that a liable tendency of koge. generation is observed by contraries.
Thus, in the heat generating section corresponding to a certain color, the upper protective layer is hardly corroded and instead, a problem of koge. property takes place. In addition to this, a phenomenon that the koge. characteristic, though hardly at issue in a former Ta, becomes noticeable on account of adopting a Ta-containing amorphous alloy never fails to occur. Incidentally, a scanty generation of koge. in a former Ta can be presumed to be attributed to the balanced occurrence of some corrosion and koge. in the former Ta and to the prevention of koge. accumulated generation due to gradual scraping by some corrosion in the Ta film surface.
With an arrangement of adopting either Ta or a Ta-containing amorphous alloy as the upper protective layer in contact with ink, as described above, full attainment of making the service life and the reliability of an ink-jet head compatible which uses highly koge. characteristic ink and corrosive ink depending to each color has become difficult.
Accordingly, in consideration of these actual circumstances, it is an object of the present invention to provide an ink-jet head substrate enabling both highly koge. characteristic ink and corrosive ink to be used, an ink-jet head using the same basis and an ink-jet recording apparatus equipped with the same head.
In order to attain the above described object, in an ink-jet head substrate, including: a heat generating resistor forming a heat generating section on a base; an electrode wire electrically connected to the heat generating resistor; and an anti-cavitation film installed via an insulator protective layer on the above heat generating resistor and the above electrode wire, the present invention is characterized in that the above described anti-cavitation film is formed of materials varying with individual given areas on the base.
Besides, in an ink-jet head with a plurality of liquid paths communicating with discharge ports for discharging ink droplets installed corresponding to heat generating sections for supplying different types of ink to individual several flow paths on an ink-jet head substrate which comprises: a heat generating resistor forming a heat generating section on a base; an electrode wire electrically connected to the heat generating resistor; and an anti-cavitation film installed via an insulator protective layer on the above heat generating resistor and the above electrode wire; the present invention is characterized in that the above anti-cavitation film is formed of materials varying with individual areas corresponding to types of ink on the base.
Besides, in an ink-jet head substrate, including: a heat generating resistor forming heat generating sections on a base; an electrode wire electrically connected to the heat generating resistor; and an anti-cavitation film installed via an insulator protective layer on the above heat generating resistor and the above electrode wire, the present invention is characterized in that the above described anti-cavitation film is divided into films varying in ink corrosion resistance every predetermined area on the base.
Besides, in an ink-jet head substrate, comprising: a heat generating resistor forming a heat generating section on a base; an electrode wire electrically connected to the heat generating resistor; and an anti-cavitation film installed via an insulator protective layer on the above heat generating resistor and the above electrode wire; the present invention is characterized in that the above anti-cavitation film is divided into films varying in ink corrosion resistance with individual given areas on the base.
In a head substrate and an ink-jet head according to the present invention as mentioned above, the above anti-cavitation film is preferably divided into a Ta film or a TaAl film and a Ta-containing amorphous alloy film for each of the above-mentioned areas.
And, the above Ta-containing amorphous alloy is preferably composed of Ta, Fe, Ni and Cr and those expressed in terms of Composition Formula (I):
Taxcex1Fexcex2Nixcex3Crxcex4xe2x80x83xe2x80x83(I),
wherein 10 at. %xe2x89xa6xcex1xe2x89xa630 at. %, xcex1+xcex2 less than 80 at. %, xcex1 less than xcex2, xcex4 greater than xcex3 and xcex1+xcex2+xcex3+xcex4=100 at. %, are preferred as amorphous alloys.
At heat generating sections of areas in which easily koge. generating ink is used on a head substrate, according to such a composition of the head substrate and the ink-jet head, since use of Ta as a material of the anti-cavitation film in contact with ink suppresses the accumulated generation of koge. on account of a little-by-little scraped anti-cavitation film accompanying an increase in heater drive pulse, the efficiency of bubbling does not decrease. On the other hand, at heat generating sections of areas to which strongly corrosive ink is applied on the head substrate, a Ta-containing amorphous alloy is used as a material of the anti-cavitation film, so that hardly any corrosion takes place. Thus, in case of using a plurality of heat generating sections arrayed in a straight line on the head substrate divisively for different types of ink, the head substrate can attain a sufficient service life and the reliability compatibly for both following types of ink even if ink subject to koge. and ink corrosive to Ta are included in the ink types.
Besides, the present invention also includes an ink-jet recording apparatus comprising a carriage on which to mount the above ink-jet head for discharging ink droplets from the ink-jet head to make recording while moving the carriage corresponding to recording information items.